The short of it: they will be culling through evidence, will be questioning people for the next 24-48 hours before they have a real credible picture of what happened. Until then, have a beer and stop listening to the idiots on TV news.
Should be fun to see what new “security” measures the government decides to drop on us. Maybe they’ll outlaw garbage cans and marathon runners. That’s my bit of useless speculation for the day.